Production

The first industrial acrolein synthesis in the early 1930s by Degussa, and began
production in 1942. Acrolein was first produced commercially through condensation of
acetaldehyde with formaldehyde:

The reaction runs at 300-320C in the gas phase over Na silicate/SiO
2
.
Today, this route has been replaced by catalytic oxidation of propene:

Another method to produce acrolein was discovered through has-phase oxidation of
propylene. Shell was the first company to practice and the reaction is run at 350- 400°C,
over Cu
2
O/SiC with I
2
as a promoter. Due to poor performance of cuprous oxide catalysts
and low propene conversions of up to 20%, other catalysts have been developed which is
more profitable. The discovery of new catalysts, bismuth molybdate and
phosphomolybdate by Sohio leads to various developed of new catalyst from the oxides
of the transition, alkali and alkaline earth metals. The catalysts are characterized by a
higher tolerance towards varying reaction conditions as compare to copper-based system.
Higher yields can be achieved in single pass operation by using the catalyst.
Recently, acrolein production via dehydration of glycerol has attracted new attention due
to the increase in glycerol availability as a consequence of growing biodiesel production.
Typically, process operate at 300-400°C and pressure of 1.5 – 2.5kPa. The feed gas
contains 5 -10% propene, which is mixed with air and steam. Due to low vapour pressure
of propene, high inert concentrations and steam are necessary in order to avoid explosion
before the reaction starts. The oxygen/propene molar ration is set to a value around 1.6 to
prolong catalysts lifetime.
Acrolein production via air oxidation of propylene run at 300-360°C and 1-2 bar over a
Bi
2
O/MoO
3
fixed bed catalysts. Acrylic acid and carbon oxides are the major byproducts
produced during this reaction. Minor byproducts are acetaldehyde, acetic acid,
formaldehyde and polyacrolein.
Ugine-Kuhann, the wrd’s argest acrein prducer, currenty perates a 50000tnne-
per-year plant in France using a Nippon Shokubai catalysts based on Mo, Bi, Fe, Co, W,
and other additives. The catalyst is arranged in a fix-bed tubular reactor, through which a
heat transfer liquid flows. Propene is oxidized in high conversion (96%) with an excesss
of air in the presence of steam at 350-450C and a slight pressure. A large air/propene
ration is necessary to maintain the oxidation state of the catalyst above a certain level, as
otherwise the acrolein selectivity drops. Under these conditions, the selectivity can reach
90% (based on C3H6). The byproducts include acetaldehyde, acrylic acid, and acetic acid.